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G. B. DAVIS. No. 67,782. HOT AIR FURNACE.

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G. B. DAVIS, OF CHICAGO, ILLINOIS, ASSIGNOR TO M. A. THAYER- AND W. H.BOOMER, OF SAME PLACE.

Letters'Patent N0. 67,732,,dated August 13,1867.

HOT-AIR FURNACE.

TO ALL WHOM IT MAY CONCERN:

Be it known that I, G. B DAVIS, of the city of Chicago, in the county ofCook, and, State of Illinois, have invented new and useful improvementsin Hot-Air Fhrn'acesf. and I do hereby declare that tho-following is afull andexact description thereof, reference being had to theaccompanying drawings, making partpi' this specification, in which--Figure 1 represents vertical section of the furnacealong the line M N;and

Figure 2 represents horizontal section ofthe furnace along the line M N.

The nature of my invention consists, first, in providing the hot-airfurnace with an extra heating surface;

second, in protecting the air-tubes with shields against the destructiveaction of heat; and third. in so arranging the grate as to have itshaking and dumping at the same time.

Tia-enable others skilled in theart to make and use my ingentiomi willproceed to describe its construction and operation. v

A is the outside jacket; B is the. outside drum, and C the inside drumof the furnace. D is the fire-kettle,

and E the ash-pit. .F, the 'directsmokedlue, which, when shut with adamper-,f, the smoke passing between the 7 tubes L L, ascends throughthe flues G and H. There is a separate inner drum, I, of the shape of atruncated cone, which, with the inside drum C of the furnace, makes anair-chamber, K, forming at the same time an additional heating surface.The air-tubes L L are made of wrought iron, and covfered on the sideturned towards the fire with shields l I made of cast iron, whichshields protect tlie'tubes lrom efi'ccts of heat to a great extent, andthereby preserve them for longer time The tube L having an opening, m,the air. gocs through it,

fills the space between the tube and the shield, and escaping throughthe minute opcnings an of the shield, makes the furnace a gas-burner.The shields are riveted to the tubes. The round grate O has aswivcl-loop,

S, attached to its centre b ar, by means of which it sets onthe roundedend of the grate-bar P, and has,.consequently, two motions, horizontaland vertical, so thatby means of a rod, R, it may be shaken'or dumped atwill. T T are the openings for hot-air pipes leading to registersthrough the building.

Having thus fully described my furnace, what I claim as my inventiornand desire to secure by Letters."

Patent, is I 1. The round grate O,'in combination with the grate-bar Pand swivel-loop S, all arranged and operating as and for the purpose setforth.

2. The air-tubes L L, in combination with shields ll, arranged andconstructed substantially as herein described and for the purposespecified. I r

3., The combination of the 'ainchamber K .with the shielded air-tubesL'L, substantially as set forth.

G. ,B. DAVIS.

Witnesses:

JAs. R HAYDEN, .T. B. Tunenm.

